Add a total startup counter

With this counter of all startups, you can now use metrics to compute ratios of sessions.  Also add some UMA to the tracking file.

TEST=not this time
BUG= no

Review URL: http://codereview.chromium.org/6281009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72277 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index c48dbe4d..54ee7b5 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -535,6 +535,7 @@
   // stats can be made meaningful.
   if (flags.size())
     UserMetrics::RecordAction(UserMetricsAction("AboutFlags_StartupTick"));
+  UserMetrics::RecordAction(UserMetricsAction("StartupTick"));
 }
 
 //////////////////////////////////////////////////////////////////////////////